In-situ spectroscopic studies of single -walled carbon nanotubes and conjugated polymers in electrochromic devices

Our initial focus has been the optimization of the performance of reflective electrochromic devices. In-situ reflectance measurements and extensive subsequent analysis enabled us to construct devices with significantly enhanced performance. Variable reflective electrochromic devices based on PProDOT-Me2 and PBEDOT-NMeCz were optimized to exhibit contrast ratios of 60-70 % in the mid-infrared region. In the latter region, two strong absorption peaks, O-H stretching mode and C-H stretching mode, were hindering the performance of the devices. A novel technique was developed in order to build water-free devices. In addition a new sample holder was designed that permits control of the electrolyte gel thickness, and reduces the C-H signature.;Building upon the aforementioned techniques, we designed an infrared transmissive/absorptive type of electrochromic cell. The construction of such a device had been previously impossible due to the absence of a suitable, infrared transparent, conducting material. An extensive study of single-walled carbon nanotubes as free-standing films showed that these films have the highest transmittance among transparent conductors in the 2-5 mum spectral range, at very low sheet resistance. Transmittance measurements on purified (p-doped) and vacuum annealed (de-doped) carbon nanotube films were performed and analyzed from far infrared through ultraviolet, at temperatures between 50 K-300 K. The result of this study led us to propose the construction of the very first transmissive/absorptive EC device in the infrared region using SWNTs as the conducting layer. The polymer that was used in the devices is PBEDOT-Pyr-Pyr which can be both p- and n- doped.